Method for detection and monitoring of clinker formation in power stations

ABSTRACT

Systems and methodologies for detection and monitoring of the soot build up and clinker formation in coal fired power stations in which there is disclosed early identification of soot build up and hard sintered formation and adopting corrective measures for soot cleaning by automatic cleaning events based on observed levels of heat transfer within the boiler region of the power station.

FIELD OF THE INVENTION

This invention relates to systems and methodologies for detection and monitoring the build up of soot and clinker formation in coal fired power stations.

During coal combustion in the Steam Generators (Coal driven Power Stations) as by product of such process is flying ash.

In coal, minerals are usually present as free ions, salts, organically bound inorganic and hard minerals. During process of coal combustion these minerals partly vaporized, coalesce or fragment and transforms into ash and depose on wall tube surfaces creating heat transfer reduction and possibility of clinker formation in the boiler section of power stations due to build up of high ash content, which has a low fusion temperature. The burning of low quality of coal also increases the build up of clinker material.

When the build up of soot and clinker material exceed a certain point the efficiency of the power plant is reduced and can result in the power station having to shut down in order to try to remove the clinker buildup.

This can be a very difficult and time-consuming procedure as it often involves a substantial amount of manual work to physically dislodge the clinker material.

If the cleaning methods are too vigorous to remove the clinker material this can result in damage to the internal components of the boiler, such as the pipes carrying the steam/water through the boiler.

It is therefore considered important to be able to preempt the build up of clinker material or otherwise provide a system or method providing an early warning for clinker buildup.

Ash build up mainly in radiation zone directly exposed to flame radiation resulting to slagging, while sintered deposit in convection zone not directly exposed by flame radiation called fouling.

It is an object of the present invention to overcome, or at least substantially ameliorate, the disadvantages and shortcomings of the prior art.

Other objects and advantages of the present invention will become apparent from the following description, taking in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.

SUMMARY OF THE INVENTION

This invention relates to systems and methodologies for detection and monitoring of the soot build up and clinker formation in coal fired power stations but not limited to them only.

Early identification of soot build up and hard sintered formation and adopting corrective measures for soot cleaning but not limited to it as to remove the hard ash deposits before it grows bigger in size and sinter in so called clinkers.

When early removal is not possible than to monitor clinker build up and to plan early shut down for clinker removal before it becomes to large and costly.

The Clinker Alarm System detects potential clinkers by being able to identify a number of parameters;

-   -   Heat transfer deterioration caused by soot build up, soot shape,         operating conditions and limitations (OC)     -   Acceptable Heat Flux (AHF) for particular region or minimum         acceptable heat transfer value taking in account boiler         operating conditions & limitations (OC) from one side and soot         build up and soot condition from other side, configurable per         each region;     -   The operating conditions & limitations (OC) limited by steady         state of operation, power output, burner configuration, coal         blend, coal particle size after milling, tube pressure, place in         boiler, high reheater spray flow and others;     -   AHF margins are adjusted automatically real time based on         operating conditions (OC);     -   Prolonged Low Heat Flux (PLHF) is always below AHF for         particular region and is representing heat transfer below         minimum required heat transfer for prolonged period and is         representing sintered soot build up (clinker formation) around a         particular region;     -   Soot cleaning (SC) activation based on Heat transfer         deterioration and acceptable heat transfer (AHF) margins     -   The duration for which Clinker Alarm System will consider PLHF         acceptable is also configurable.

Wherein upon detecting soot build up or potential clinkers, System prioritize soot/clinker removal for affected regions.

In the same time System is monitoring PLHF tendency over configured duration and, if after number of soot cleaning executions, PLHF value does not improve System will make decision about possibility of clinker formation

At the same time the Clinker Alarm System will also raise an alarm for further actions as deemed necessary by the user depending on user set parameters or requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of heat transfer monitoring through a monitored region of the boiler over time of the present invention;

FIG. 2 shows a schematic overview of the present invention.

By way of example, an embodiment of the invention is described more fully hereinafter with reference to the accompanying drawings and description below.

DESCRIPTION

According to the present invention, although this should not be seen as limiting the invention in any way, there is provided a system of real time heat transfer data analysis in regard for soot detection and soot growth monitoring, monitoring clinker build up and clinker growth.

The system including heat transfer data collection, data filtering and analysis obtained by any type of heat flux instrumentation or any other alternative method which is correlating with heat transfer collection (as for example thermocouples positioned on the inner side of the centre of symmetry plain of the webs and tubes on insulation side, other means of monitoring heat build up are to be included within the scope of the present invention) on various boiler places and using mathematical calculations of results as to observe deterioration of heat transfer in boiler tubes at all places simultaneously.

After the heat deteriorate to Acceptable Heat Transfer value (AHF) the system is calling for soot cleaning in this particular region

After the heat transfer deteriorate to Prolonged Low heat flux (PLHF) for period of time and after several calls for soot blowing were executed but Low heat flux value does not improve from low value than system is rising clinker alarm for that particular boiler location.

This application is covering:

-   -   Using data from heat transfer instrumentation, data filtration         and calculation in real time as to find heat transfer         deterioration     -   Principles of determining when soot build is reaching the limit         and soot cleaning should be done     -   Principles of determining when clinker alarm to be activated.

With reference to FIG. 1, this shows the real time monitoring of the heat transfer value in a region of the boiler of the coal powered power station. Over time the build up of soot cause the heat transfer value to decrease. When it reaches a predetermined level (AHF value), a cleaning routine is initiated automatically (A_(t1)).

As the cleaning sequence A_(t1) is carried out, the heat transfer value increases indicating that the efficiency of the boiler is returning. However, as time continues, once again the build up of soot begins and the heat transfer value decreases until such time as it ones again reaches the AHF level and a further cleaning sequence is initiated A_(t2).

However, depending on the soot condition in the boiler and the successes of the cleaning operation at A_(t2) the heat transfer value may continue to decrease up till low heat transfer (PLHF) value is reached. This then begins the process of timing or monitoring for a clinker alarm event.

Due that heat transfer (PLHF) value is constantly below acceptable heat flux (AHF) value System will initiate in regular time interval automatically soot cleaning sequences from point A_(t3) up till Atn

But if the heat transfer value does not excess the PLHF or continues to trend downwards over a predetermined time then this will cause a clinker alarm event.

-   -   Heat transfer

-   ∘ optimum heat transfer

-   AHF acceptable heat transfer

-   PLHF prolonged low heat transfer

-   t heat transfer deterioration time

-   t_(sc) cleaning time

-   T (PLHF) clinker monitoring time

-   A_(t1) start first cleaning time     -   A_(tn) (n) number of cleaning time events     -   S start of PLHF monitoring

FIG. 2 shows the overview of the working of the present invention of a method of monitoring and detecting conditions in relation to the formation of soot build up and clinkers in the boiler section of a coal powered power station.

The flow diagram of FIG. 2 shows an instrumentation (module 1), a data processing (module 2), a clinker detection (module 3), soot cleaning (module 4) and an interface monitoring (module 5).

Additionally, I (heat transfer instrumentation), I_(N) (instrumentation condition), I_(C) (instrument calibration condition), OC (Operating condition), AHF (acceptable heat flux), SC (soot cleaning), HF (heat transfer deterioration monitoring module), PLHF(prolonged low heat transfer module)

Using heat transfer real time measurement through a boiler tube or any correlated method which replaces heat transfer from furnace flame up till tube surface as to monitor heat transfer deterioration.

Using data filtering and mathematical interpolation as to establish Heat Transfer Deterioration (HTD) tendency in real time as to monitor when HTD will reach Acceptable Heat Flux (AHF) margins and Prolonged Low Heat Flux (PLHF) margins, for each particular region.

Heat transfer deterioration (HTD) and margins of each AHF, separately for each region, are adjusted automatically in real time based on operation conditions & limitations (OC) as are transition or steady state of operation, power output, burner configuration, coal blend, milling coal particle size, tube pressure, place in boiler and level of high reheater spray level etc.

PLHF trend value is always less than AHF value for each particular region.

PLHF trend value is a trend value of a constantly unchanged heat transfer tendency for duration of configurable time frame and number of mechanically successful soot cleaning executions (Execution must happen during that configurable time).

The soot cleaning execution strategy is integrated part of clinker alarm monitoring system, triggered when heat transfer deterioration value reaches AHF value, for at least one segment in the region.

Soot cleaning execution strategy is covering a selection of cleaning devices, creation of priority list for execution, monitoring execution results etc

Prior to the clinker alarm being raised, there is a final execution of furnace cleaning (A_(tn)) regardless of HTD, AHF or PLHF values (safety issue)

The Clinker alarm can be identified to the operator as a blinking red dot on the operators interface screen but not limited to it, representing potential clinker formation at particular boiler region.

Using interface screen and schematic boiler configuration with all positions of heat transfer instrumentation is allowing operators to monitor clinker formation and direction of growth in real time and sound an alarm and advise operators so that other action can be taken as deemed necessary. 

1. A method of controlling soot build up, soot cleaning and build up of clinkers in a coal powered power station, the method including the steps of: obtaining real on line measurement of heat transfer data, in data analysis using data filtration, operating conditions and limitations (OC) and mathematical interpolation as to correlate soot build up, clinker formation with heat transfer deterioration. selecting an acceptable Heat Flux (AHF) value, as a minimum value up till which heat transfer deterioration trend can go, before soot cleaning will take place for at least a first region in an interior of the boiler; selecting a prolonged Low Heat Flux (PLHF) value for at least the first region in an interior of the boiler; initiating a predefined soot cleaning event A_(t1) in the at least a first region in an interior of the boiler when the heat transfer deterioration value equals the pre-selected AHF value and monitor results of soot cleaning; monitoring the heat transfer deterioration value when heat transfer value is equal to PLHF as to initiate calculation of a clinker monitoring time (tPLHF); and automatically initiating soot cleaning event A_(t2) based on Heat Transfer Deterioration and AHF value and after that number of soot cleaning events on the same bases up till (and including) A_(tn) at least at first region in an interior of the boiler during which heat Transfer Deterioration trend is towards the PLHF value.
 2. The method of claim 1, further characterized in that after the further predefined cleaning event A_(tn) if the heat transfer value is still PLHF then activating an alarm means.
 3. The method of claim 1 further characterized in that at least one of the variables for Heat Transfer Deterioration or AHF or PLHF is dynamically calculated.
 4. The method of claim 3, wherein dynamically calculation and data filtration is based on at least one of the variables selected from the group consisting of operating conditions and limitations (OC) as are Steady State of operation, Power Output of the power station, Burner configuration of the boiler, Coal blend, Coal particle size, Tube pressure in the boiler tube, Place in the boiler, High Reheater spray flow but not limited to this only.
 5. An system when used for monitoring heat transfer deterioration in a coal powered utility stations boiler, controlling soot cleaning and determining build up of clinkers in the combustion chamber and boiler region, wherein the system uses the method of claim
 1. 